IPP Mail Archive: Re: RE: IPP> New IPP Model Document

IPP Mail Archive: Re: RE: IPP> New IPP Model Document

Re: RE: IPP> New IPP Model Document

Scott Isaacson (SISAACSON@novell.com)
Fri, 29 May 1998 17:34:39 -0600

Carl,

You provide good examples of why two URLs might refer to the same IPP =
object yet might be literally different (this gets back to the classical =
problems with equality - syntactically, semantically, instance vs class, =
type vs value, etc). Do we need to put any of them in the document as =
examples?

Can we live with the fairly simple statement that is in the document:
" 2. Even though these two URLs might not be literally identical (one =
being relative and the other being absolute), they must both reference the =
same IPP object."
or is the statement too simple?

I also think that most of the text that I added to the model document on =
this subject should be moved to the encoding and transport document. The =
model document should not care about all of the reasons why 2 HTTP URLs =
might not be identical and yet refer to the "same" resource. What do you =
think?

Scott
=20

>>> Carl Kugler <kugler@us.ibm.com> 05/29 4:59 PM >>>
Speculation: they might also be different:

After TLS negotiation?

Where the URIs are semantically the same but syntactically different, =
e.g.:
- Absolute vs. Relative
- host.domain vs dotted-ip
- Default port specified vs. port omitted
- UPPERCASE/lowercase in hostname
- URI translation using equivalent escape codes

After an HTTP redirect handled automatically by an HTTP layer in the =
client
stack that doesn't know about IPP?

Maybe an HTTP proxy server handles a redirect invisibly to the client?

owner-ipp@pwg.org on 05/29/98 04:13:56 PM
Please respond to owner-ipp@pwg.org=20
To: jkm@underscore.com=20
cc: ipp@pwg.org=20
Subject: RE: IPP> New IPP Model Document

Absolutely, I see the advantage of having the IPP information take
precedence, I'm just not sure of the impact of having the two headers
(HTTP and IPP-body) be different, and actually getting this to work in a
CGI/NSAPI/ISAPI-based implementation.

The generic web server will dispatch to the HTTP header-specified URI
(I'm assuming, someone correct me if this is not the case). Once this
dispatch occurs, the target in the HTTP header better be able to handle
whatever is coming in the application/ipp body part. In this scenario,
its too late to apply any precedence.

Has someone identified a case where the two headers have to be
different? (I may have missed some email...)

Randy

-----Original Message-----
From: Jay Martin [SMTP:jkm@underscore.com]=20
Sent: Friday, May 29, 1998 2:51 PM
To: Turner, Randy
Cc: ipp@pwg.org; Puru Bish
Subject: Re: IPP> New IPP Model Document

Randy,

> This may be a difficult requirement to meet if an IPP
implementation is
> built as an extension to a generic web server (like Apache).

Are you sure about this? I mean, I can see you point to
a certain extent, but wouldn't it be advantageous for an
IPP server implemented as a front-end on a generic platform
to be used as a multiplexor to several Printers and Jobs?

On the other hand, if the HTTP request header takes precedent,
then why are we specifying printer-uri/job-uri at all at the
IPP protocol level? Aren't we asking for trouble when the
HTTP request header and the corresponding IPP attributes don't
match (with regard to interoperability)?

...jay

----------------------------------------------------------------------
-- JK Martin | Email: jkm@underscore.com=20

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----------------------------------------------------------------------

Turner, Randy wrote: > > This may be a difficult requirement to meet if an IPP implementation is > built as an extension to a generic web server (like Apache). > > Randy > > -----Original Message----- > From: Jay Martin [SMTP:jkm@underscore.com]=20 > Sent: Friday, May 29, 1998 2:34 PM > To: ipp@pwg.org=20 > Cc: Puru Bish > Subject: Re: IPP> New IPP Model Document > > After thinking about this, I tend to agree with Puru's > statement: > > >From "Tom Hastings" > > > > :: In fact, the HTTP request header URI, if persent, takes > precedence" > > (over printer-uri/job-uri operation attributes). > > > > I think it should be the other way around. I feel the > > printer-uri/job-uri, supplied by IPP client, should have > higher > > precedence to an IPP server than the HTTP header URI. > > ...jay > > > ---------------------------------------------------------------------- > -- JK Martin | Email: jkm@underscore.com=20 > -- > -- Underscore, Inc. | Voice: (603) 889-7000 > -- > -- 41C Sagamore Park Road | Fax: (603) 889-2699 > -- > -- Hudson, NH 03051-4915 | Web: > http://www.underscore.com -- > > ----------------------------------------------------------------------